1. Field of the Invention
The present invention relates to magnetic heads, particularly magnetoresistive heads performing well even for high magnetic recording density, a method of producing these heads, and magnetic read/write devices.
2. Description of the Related Art
Magnetic recording disk drives which are commonly used now employ read/write separate heads; that is, recording is performed by an inductive thin film head and reading back is performed by a magnetoresistive head. The magnetoresistive head uses the magnetoresistive effect that electrical resistance changes, depending on the external magnetic field. is shown in FIG. 2, the magnetoresistive head is comprised of a magnetoresistive element consisting of a magnetoresistive layer 14, magnetic domain control layers 15, and electrodes 16; upper and under layers 12, 18 and elements for blocking out an unnecessary magnetic field, one of which forms a layer covering the magnetoresistive element and the other forming an under layer; and upper and under gap layers (insulating layers) 13, 17 for isolating the magnetoresistive element from the shield layers, wherein A1203 films are mainly used as the gap layers (insulating layers).
As recording density is becoming denser, the spacing between the upper and under layer decreases accordingly, and consequently, the thickness of the insulating gap layers, each inserted between the magnetoresistive element and each shield, becomes thinner. Consequently, static electricity or electrical stress causes overcurrent to flow between the electrodes of the magnetoresistive element or between the magnetoresistive element and each shield, making the magnetoresistive element liable to break down. To address this trouble, some methods for improving the dielectric strength by grading up the quality of the insulating layers have been disclosed; e.g., a method of laminating SiO2 and Si3N4 layers, set forth in Japanese Patent Laid-Open Publication No. Rei 6-52517 and a method of aluminum oxidation by heat application, set forth in Japanese Patent Laid-Open Publication No. Rei 9-198619. Moreover, some methods for bypassing overcurrent so that it will not flow across the magnetoresistive element or between the magnetoresistive element and each shield have been disclosed; e.g., a method of connecting the magnetoresistive element to the ground basis by Schottky diodes, set forth in Japanese Patent Laid-Open Publication No. Rei 7-169005; and a method of connection using varistor material set forth in Japanese Patent Laid-Open Publication No. Hei 8-45033 and Japanese Patent Laid-Open Publication No. Hei 11 265503.